xmartin



T. G. MARTIN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 12. I91?- Patented @aept. 16, 1919..

4 SHEETSSHEET I.

T. G. MARHN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR-12.1917.

T. G. MARTIN.

TELEPHONE EXCHANGE SYSTEM.

APPLICAHON FILED MAR, 12, 1917 l y 53 11 MT 1L 9 MIN 1 w Patented Sept. 16, 1919.

4 SHEETS-SHEET 3.

T. G. IWARTEN. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR-12. 19H- Pammed mm, 16, 1919.

4- SHEETS-SHEET 4.

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STATES PATENT OFFICE.

TALBOT G. MARTIN, O15 CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORlPORAIION OF ILLINOIS.

Specification of Letters Patent.

Patented dept. ltd, lllltl.

Original application filed May 6, 1910, Serial No. 559,814. Renewed December 30, 1916, Serial No. 139,904. Patent No. 1236,8158, dated August 14, 1917. Divided and this application filed March 12, 1917. Serial No. 15 L156.

To all whom it may concern:

lle it known that l, TALBOT l". MARTIN, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful limprovement in 'lelephone-Exchange Systems, .of which the following is a specification.

My invention relates to telephone systems in general, but more particularly to auto matic or semi-automatic systems, as it may be. used in systems in which the connection is entirely automatic, or in systems in which a calling connection is established by means or both manual and automatic apparatus.

It also relates, more specifically considcred, to measured service systems-that is to say, systems in which some provision is made for assessing toll tor each successful call, either by the use of a coin or check-controlled mechanism at the substation, or by the use of a registering mechanism located either at the substation or the central station.

My invention contemplates, for example, a system in which the said connectors are provided with means for reversing the talking current in a portion of the talking circuit, when the called subscriber answers, for any suitable or desired purpose.

It also contemplates a systeinin which automatic connectors and repeaters are employed. the said connectors being provided with means for including resistance in series with a portion ot the line or talking circuit when the called line is found, and the said repeaters being provided with similar means fol-including resistance in series with another portion of the talking circuit when the called line is found, whereby a. supervisory signal is displayed at the cord circuit or the originating operator, indicating that the connection has been completed, which signal is then retired when the called subscriber answers.

It further contemplates a system in which called subscriber not only retires the said signal to show that the call has been answered, but also serves to operate a measured service device, such as a registering mechanism, which measured service, device can 'be located at any suitable point in the connection, as will hereinafter more tullv appear. a

My invention also contemplates a rotary connector, 6., a connector having means for automatically selecting an idle one of a group of lines, having provisions for reversmg the current in the calling side of the talking circuit when the called subscriber answers, for any suitable or desired purpose.

It also contemplates certain novel details and combinations and features of improvement tending to increase the general ctiiciency of a telephone exchange system of this particular character, as will hereinafter more fully appear.

' In the accompanying drawings Figure 1 IS a dlagrammatic view of a portion of the apparatus used in a telephone system embodying the prmciples of my invention. The apparatus shown in this figure consists of the automatic subscribers substation It allotted toa line which terminates in the line switch C, there being a master switch I) for controlling the plungers ot the group of line switches of which the switch (l'is a member A meter is also shown at J for registering the calls made by the substation A. At E is shown a first selector, which is one of a group allotted to the trunk lines which are accessible to the rrroup ot line switches of which the switch (,1 is a i'ncmbcr.

Fig; 2 is a similar view of a repeater ll and a second selector switch It, this switch being quite similar to the first selector lfl.

l ig, 3 is a diagrammatic view oi a con nector ll, line switch C which is similar in construction to the line switch t, and substation rlr which is similar to the substation it.

Figs. l, El and 8 taken together represent a complete circuit connection established between the two subscribers substations It. and lit.

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ll lid Fig. 4 is a diagrammatic view of a rotary connector'I' which can be used in a system embodying the principles of my invention.

Fig. 5 is a similar view of a manual telephone, together with a suitable cord circuit for connecting to the automatic apparatus referred to in the foregoing figures.

' The substation A may be of any suitable or approved type and comprises the usual receiver 2, transmitter 3, switch hook 4, impulse springs 5 and '6, impulse wheel 8, which is secured to a dial (not shown) by means of the shaft 9, ringer 10 and condenser 11.

The line switch C is of the general type disclosed in British Patent No. 26,301 of 1906, and in the American Tele hone J 0m"- nal of June 6, 1908. This switch is provided with the usual plunger (not shown) attached to the plunger arm 19 which is adapted to be attracted b the magnet 14. This magnet comprises our windings, a line windin 15, a trip or pull-in winding 16, a cut-o winding 17 and an auxiliary winding 18. The magnetic circuit of the winding 16 and 17 is separate from that of the windings 15 and 18, so that the plunger arm 19 and cut-off armature 20 are afi'ected only by the windings 16 and 17, while the windings 15 and 18 control only the armature 21. The winding 16, when energized attracts'both the plunger arm 19 and cut-ofi armature 20, while the winding 17 is strong enough to operate only the cutoff armature 20, but will holdthe plunger arm in an operated position after the winding 16 deenergizes. The attraction of the plunger arm 19 by the magnet 14: causes the plunger of the switch to be thrust lnto a group of springs to force the springs 22, 23, 24, 25 into engagement with the springs 26, 27, 28 and 29, respectively, whereby the line conductors are extendedover trunk lines to a selector switch such as the selector E, Fig. 1. Although only one set of springs 1s shown, each switch .C is provided wlth a number of such sets, each set formin the terminal of a trunk line leading to a se ector switch. The plungers of the group of line switches of which the switch C is a member are controlled by a common mechanism D usually called a master switch. This master switch controls the plungers in such a manner that the plungers of all idle line switches always stand in readiness to engage the terminal of an idle trunk line leading to a selector switch. The meter shown at J is individual to the substation A and registers only when the subscriber who has been called by the substation A answers. It comprises the ratchet wheel 61 which is actuated by a pawl on the end of'the armature 62, which armature is controlled by the relay 63. This relay is composed of the two windings 64 and 65, either one of which alone will not attract the armature 62, but will hold it in its operated position after it is once attracted.

The master switch D comprises a motor magnet 30 which operates the ratchet wheel 34, a bank of contacts a and a number of circuit-controlling relays. The lnaslcr switch bank a is provided with a wiper 40 for keeping some one of the individual segments .38, 39, etc, in electrical connection with the common segment 41. By means of a suitable mechamcal connection the rotary motion of the ratchet wheel 31 is transmitted to the plunger shaft, giving said shaft an oscillatory motion to move the idle plungers (which, when normal, are in locking engagement with said shaft) back and forth in front of the bank terminals. To the plunger shaft there is rigidly secured a cam or locking plate 33 having on its surface a number of circular openings 36 which are engaged by the pin 33 on the armature 37.

The openin s in the cam 33 are so positioned that t 1e pin 35 can engage an open ing only when the plungers that are in engagement with the plunger shaft are directly opposite the terminals of a trunk.

The selector switch E is of the general type disclosed in United States Letters Paient No. 815,321, granted March 13, 1906, to

Keith, Erickson & Erickson, but. as here shown, is adapted to operate in conjunction with a two-wlre system. Among other details the selector comprises a set of wi )crs -16, 47 and 48 carried upon a shaft luot shown) which has a vertical motion controlled by the vertical magnet 19 and a rotary motion controlled by the rotary ma mate. The selector also has the usual sh e switch comprising the wipers 51, 52 53 and 54. The side switch is controlled bv the private magnet The operation of the switch is controlled by the calling subscriber through the medium of the doublc-wouml line relay 56. The release magnet 57 is normally disconnected from battery by the separatiou pf springs 58 and 59, which are held out of engagement by the arm 60 as long as the switch shaft is in its lowest position. The mechanism of the selector F.

'is released immediately by the energization of the release magnet, rather than by its dei nergization, as shown in said sclcctor patent.

The repeater shown at F, Fig. 2. is used as a means of repeating impulses which are transmitted from a substation of one exchange to operate switches in another exchange. the double-wound line relay 68 and slow relays 69 and 70. The relay 70 operates to cut the condensers out of the circuit, while the impulses are being repeated. The repeater Among other details it comprises antenna also comprisesthe high resistance relay 71 and the doublewound relay 72.

The selector H, also shown in Fig. 2, is similar to selector l5 shown in Fig. 1.

The connector l is of the type disclosed in United States Letters Patent #815 176, granted March 13, 1906, to Keith, Eric son & Erickson, but, like the selectors E and H, is adapted to operate in a two-wire system. Like the selectors, the connector has a double-wound line relay 73, vertical magnet 74:, rotary magnet 75, private magnet 76 and a side switch. In addition, the connector is provided with a back-bridge relay 77, through which the called subscriber is supplied with talking current, a ringer relay 78, by means of which the generator L may be connected across the line, a high resistance relay 79, a lousy locking relay 80 and a current-reversing relay 81. The busy signaling machine U consists of an interrupter 82 and induction coil 83.

The rotary connector I is similar in con struction to the connector I, but difiers from i it slightly as to circuits and manner of operation. When the wipers of connector 1 are brought into contact with a desired line in response to the operation of the substation calling device, and it said desired line is busy the wipers of the connector 1 remain upon the contacts of the called line, but connection is not completed with the said line and the calling subscriber is given a busy signal. l then the wipers of connector 1' are brought into contact with a busy line, said 7 wipers do not' remain in this line, but are automatically rotated to the next or an idle set of contacts. In thls way the lines which -are connected to the banks of connector ll may be divided into a number of roups, all lines of any group being accessib e by calling the number of the first line of said group. The set or bank contacts immediately preceding the contacts of any group of lines is connected to relay 276 and resistance coil 277. as shown in Fig. 4.

The substation A and line switch C are similar to substation A and line switch C of Fig. 1.

As shown in these drawings, there are a number of batteries 15, with the positive ter minal preferably grounded at G, for supplying the exchanges with the necessary current for talking and operating purposes; but, of course, in actual practice this number may be changed and the arrangements modifiet' in any suitable manner -that is, one battery may be used for operating one exchange and another battery for operating another exchange. Obviously any number and any combination of batteries may be used. depending upon the conditions to be met.

Having thus described the general cha actor of the apparatus which is used in the system, 1 will now describe the process by which the subscriber at substation A establishes connection, signals and converscs with the subscriber at substation A, whose number we will assume to be 1 will also describe how a call is registered on the meters and the method by which the apparatus is restored to normal condition after the conversation is completed.

ll will also describe how the subscriber at substation A may obtain connecting; with an automatic substation.

In order to call #2220 the subscriber atsubstation A must remove his receiver and operate his dial once for each of the four digits 2-2-20. its soon as the receiver is removed from the hook the ringer circuit, which is normally bridged across the line, is broken by the separation of the springs 85 and 86, but a circuit is completed through the transmitter and receiver in series by the closing of the springs 85 and. 87. lhe engagement of these springs completes a circuit through the line winding 15 of the line switch G. This circuit extends from ground G through the springs 88 and 89, line conductor 12, springs 85 and 87, impulse springs 5 and 6, receiver 2, trans-- mitter 3, conductor 13, Springs 91 and 90, line winding 15 of the magnet l-i, contact 96 and armature 87 to the battery lead 97. The armature 21 of the magnet 14: is attracted upon the energization of the line winding 15, thereby closing the springs 93 and 88 into contact. The closure of these two springs completes the circuit of the pull-in winding 16 in series with the auxiliary winding 18, said circuit extending from ground G through the springs 88 and 93, pull-in winding 16, auxiliary winding 18 to the battery lead 97. lllne winding 16, upon energizing, attracts the armature 20 which separates the springs 89 and 91 from the springs 88 and 90, respectively, thus opening the circuit of the line winding 15. The armature 21 cannot fall back, however. until the winding 18 is short-circuited through the springs 107 and 109 by the operation of the plunger arm 19, which may be a little slower in its action than the relay armature 20. The attraction of the plunger arm 19 also serves to thrust the plunger in the batik of springs, closing the springs 22, 23, A and 25 into contact with the springs 26, 27, 28 and 29, thus extending the line conductors 12 and 13 to the selector E, as previously explained. As soon as these conductors are extended, however, a circuit is completed through the double-wound line relay 56 of the selector. This circuit extends from ground G through the lower winding of the rela 56, side switch'wiper 54 (in first positiong, springs 29 and 25, conductor 19 lllt lid

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through the substation A. in the manner previously described, back over conductor 13, winding 64 of the meter magnet 63, springs 22 and 26, side switch wiper 51 and upper winding of the relay 56 to the battery lead 97, thence through battery B to ground G. The energization of the relay 56 shifts the spring 98 out of engagement with the spring 99 and into engagement with the spring 100. This serves to close the circuit of the release relay 101. This circuit extends from ground G through the springs 99 and 100 and relay 101 to the battery lead 97, thence through battery B to ground. G. The energization of the relay 101 shifts the spring 103 out of engagement with the spring 102 and into engagement with the spring 104,'and also closes the springs 105 and 106 into contact. The engagement of the springs 105 and 106 closes an energizing circuit through the holding winding 17 of the magnet 14: of the line switch C. This circuit extends from ground 1 through the springs 106 and 105, springs 27 and 23, through the holding winding 17 to the battery lead 97, thence through battery B to ground G. The energization of the winding 17 serves to hold the armature 20 and plunger arm 19 in an operated position (as they have not yet been released, due to the slow action of armature 21.)

While the plunger arm 19 is in its operated position it holds springs 107, 108 and 109 in engagement, which short-circuits winding 18, as has been explained, and also rovides an energizing circuit for the winding of the meter relay 63. This circuit extends from ground G through springs 106 and 105 of the relay 101 of selector E, line switch hank springs 27 and 23, winding 65 and springs 108, 109 and 107 to batterylead 97, thence through battery B to ground G. The current in Winding 65 is at this time opposed by the current in winding 64: and the meter is not operated.

The energization of relay 101 also serves to place a guarding potential upon the pri vate bank contact of the calling line in the banks of all of the connector switches which have access to the group of lines of which that of substation A is a member. The contacts of the connector banks of the said group are multiplied, so that a guarding po tential placed on one contact of one connector bank will also be placed on the same contact of the banks of all the connectors of said group. This guarding potential extends from ground G to the line switch bank spring 23, as has been previously traced, and thence over conductor 110 to the connector private bank contacts.

Let us return now to the operation of the master switch D when subscriber A moves his receiver. ts has been stated, he

plunger forces spring 24 into engagement with the spring 28, which completes an energizing circuit through the master switch rclay 31. This circuit extends from ground Gr through springs 24, 28, segment 38. wipcr 40, common segment -ll. through relay 31 to battery. The relay 31, upon energizing, completes an energizing circuit through rclay 32, which attracts its armature 3T. pulling the pin 35 from the opening in the locking plate 33. It also closes an energizing circuit through the motor magnet 30. This circuit extends from ground G through the motor magnet 30, interrupter springs 43 and 42, contact )oint 111 and arnuitui'c 3T to battery lead 91', thence through battery B to ground G. As the armature H is altracted it breaks the circuit of the said mugnet 30, causing a buzzer action thus giving the ratchet wheel a step-hy-step rotary motion. The motion of the ratchet wheel is transmitted to the plunger shaft, which operates to move the idle plungcrs from the position in front of the trunk seized by the line switch C. After the plungcrs have moved a short distance the wiper 40. which is attached to the plunger shaft, is moved oil the segment 38. which corres )onds to the trunk seized by the line switch i1 lVhen the wipcr l0 leaves the contact 238 the relay 31. and consequently the relay -32, is deenergizcd. but the armature 37 cannot, fall back because the opening in the cam 33 which was formerly engaged by the pin ii) has passed out of register therewith. Thus. the master switch will continue to operate until the next opening in the cam passes under the pin 35, when the said pin will drop into the opening, thus locking the shaft against further movement, and the ulillullllc 3T disengages from contact point 111. thus opening the circuit of the magnet 3 ll the next trunk after the one seized by [he linc switch C had been busy the wipcr 40 would have found the corresponding contact. contucl Silk for instance, guarded. and would havc'muiutaincd the circuit of the relays 31 and 33 while the next opening in the cam was pas ing under the pin 3.1 Thus, lhc master switch would have continued to zldYuiicc the plungcrs past the busy trunk. The armature 37 also operates to disconnect the baltery from the line winding l5 oi all of the switchcs (l which are controlled by the ma tor switch I). and to connect the busy signailing uuichine with all of the idle lines through their line windings 15 and springs 90 and 01. i

The foregoing operations take place immcdiatcly upon lhc removal of the rcceivdi' from the hook at the calling substation and before the impulses are sent in for the first digit of the desired number. Tihen the calling device is operated {or the first digit 7'3 the impulse springs 5 and 6 are separated twice m mentar1ly. The separation of the springs 5 and 6 breaks the energizing circuit of the line relay 56 of the selector switch E.

the momentary breaking of its circuit at the springs 98 and 100. Therefore, the circuit through the vertical magnet extends from ground G through the springs 98 and 99, 103 and 104, slow relay 112, vertical magnet -19 and side switch wiper 52 (in first position) to the battery lead 97, thence through battery B to ground G. The slow relay.112 operates to close an energizing circuit through the private ma net 55. This circuit extends from ground (i through the springs 113 and 11a and private magnet 55,130 the battery lead 97, thence through battery B to ground G. The relay 112 being slow does not deenergize during the momentary breaking of its circuit as the digit 2 is being called. The vertical magnest operates twice to lift the shaft (not shown) two steps, carrying the wipers 16, 17 and 48 opposite the second-level of bank contacts, which level contains terminals of trunk lines leading to repeaters F. As soon as the shaft leavesits lowest position the arm 60 is lifted from the spring 59, allowing spring 59 to come into contact with spring 58 to provide the release magnet 57 with a battery connection. After the last impulse is delivered to the vertical magnet 49 the relay. 112 has timeto deencrgize, thereby breaking the circuit of the private magnet 55 which controls the side switch. As this magnet deenergizes it permits the side switch wipers to pass to second position. In second position the side switch disconnects battery from vertical magnets and completes an energizing circuit through the rotary magnet 50 in series with theslow acting guarding relay 115. This circuit extends from ground G through interrupter springs 116, rotary magnet 50, slow relay 115 and side switch wiper 52 to battery lead 97, thence through battery B to ground (it. The rotary magnet armature operates once to rotate the wipers 16, 17 and 18 one step onto the bank contacts, to press down the private magnet armature, and to open its own circuit at the interrupter springs 116. The circuit of the rotary magnet being thus opened. the rotary armature falls back. llf the first trunk upon the contacts of which the. wipers have just been rotated is not busy, theprivate armature will also fall back, permitting the side switch to pass to third position; but, however, if the first trunk is already in use, the private wiper at? finds the first contact grounded, and thus completes an energizing circuit through the private magnet, locking the side switch in second position, thus permitting the rotary magnet to once more energize and denergize, stepping the shaft wipers onto another contact. The locking circuit of the private magnet 55 extends from the grounded private bank contact over wiper 17, through side switch wiper 53 (in second position) and through magnet 55 to the battery lead 97. The rotary magnet continues to advance the wipers step by step until the private wiper t7 engages the non-grounded contact of an idle trunk, whereupon the private magnet 55 deenergizes and allows the side switch to pass from second to third position. When the. side switch leaves the second position thewiper 52 breaks the operating circuit of the rotary magnet.

The relay energizes in series with the rotary magnet, but, being slow acting, remains energized for a short time after the rotary magnet has deenergized for the last time. Thus the seized trunk is provided with a guarding potential the instant that the side switch passes to third position. Thus guarding potential extends from round G over springs 118 and 119, side swltch Wiper 53 and private wiper 4:7 to the private bank contacts. When the side switch wipers 51 and 54 pass from second to the third position the line relay 56 ofthe selector E is disconnected from the line, and the trunk lines 13 and 12 are extended by means for the trunk conductors 120 and 121 to the repeater 1* of Fig. 2. The circuit is then completed through the double-wound line relay 68 of the repeater 1*, said circuit extending from ground G through springs 122 and 123, lower winding of relay 68, springs 124 and 125 to trunk line 121, over said trunk line, shaft wiper 48, side switch wiper 54c and then over the same circuit through substation, as

was previously traced, back through side' switch wiper 51, shaft wiper 4C6, conductor 120, springs 126 and 127, and through the upper windin of relay 68 to battery lead 97, thence throug 1 battery B to ground Gr. The relay 68 energizes and closes the circuit of relay 69. This circuit extends from ground 1 through springs 128 and 129 and relay 69 to batterylead 97-. The engagement of springs 130 and 131 by the energization of relay 68 closes an energizing circuit through the double-wound relay 132 of the selector H. This circuit extends from ground G through lower winding of relay 132, side switch wiper 133, conductor 134. conductor 135 to and through springs 130 and 1311, re-

'lay 136, upper winding of relay 72., conductor 131', conductor 138, side switch wiper 139.,

upper winding of relay 132 to battery lead 14 O, thence through battery to ground. Relay 136 energizes to short-circuit relay 71 by closing springs 141 and 142, thus placing ground G on the opposite side of relay 71 from ground G \Vhen the relay 69 energizes upon the closure of its circuit by the energization of relay 68, a circuit is closed extending from ground G through springs 122 and 143 and through the lower winding of relay 72 to the battery lead 67. Although both windings of relay 72 now carry current, the relay is not operatively energized, because the current flows through its windings in opposite directions at this time. The engagement of springs 122 and 143 of the relay 69 also provides a new guarding potential for the selector private bank contacts of the trunk, and provides a holding circuit for the release relay 101 of the.selector E as soon as the guarding relay 115 deenergizes. This circuit extends from ground G through springs 122 and 143 to the selector private bank contacts, thence over private wiper 47, through side switch wiper 53, springs 119 and 114 of relay 115, and through relay 101 to battery lead 97. The relay 101 is slower to dener gize than the relay 115, so that this latter circuit is closed before relay 101 has time to deenergize. The energization of the two relays 69 and 136 of the repeater F shifts the holding ground of relay 68 from ground G to ground G Theapparatus is now in readiness to receive the impulses from the substation for the second digit 2. These impulses are repeated by the repeater F to the selector H, which operates to raise its shaft and wipers 144, 145 and 146 two steps and stop the same opposite the second row of bank contacts. The operation is as follows: The circuit of the line relay 68 of the repeater F is broken twice in response to the operation of the substation dial for the digit 2, thus permitting the said relay 68 to twice momentarily deenergize, causing an energizing circuit to be established through the relay 70, which immediately energizes. This circuit extends from ground G through springs 128 and 148, springs 149 and 150, 152 and 151 and relay to battery lead 97, and thence through the battery B to ground G. The relay 69 being slow acting does not deenergize during the momentary interruption of,

its circuit at the springs 128 and 129. The

energization of relay 70 serves to disconnect the condensers 153 and 154 from the conductors 138.and 134, and also serves to short circuit the relay 136 and upper winding of relay 72 by the engagement of springs 155 and 156. The engagement of springs 157 and 158 supplies the ground connection to replace the ground G which is disconnected by the denergization of relay 136 when it is.

relay 68 breaks the circuit of the selectorline relay 132 by opening the bridge across the trunk conductors 138 and 134. Since the digit called is 2, the circuit of relay 132 is thus broken twice momentarily. The re lay 70 of the repeater being slow acting remains energized during the entire time impulses are being repeated, and thus maintains the short-circuit of relay 136 and upper winding of relay 72 to prevent them from being included in the operating circuit of relay 132. Each time the relay 132 is deenergized a circuit is closed extending from ground G through springs 160 and 159, 163 and 162, slow-acting relay 164, vertical magnet 147 and side switch wiper 165 to the battery lead 140, thence through the battery 13 to ground G. The verticalmagnet 147 is thus energized twice, and operates to raise the switch shaft and wipers carried thereby tw steps. As soon as the shaft is lifted from its lowest position the arm 168 is lifted, allowing spring 169 to engage spring 17 0, which puts battery on one Side of release magnet 167. The energization of relay 164 completes an energizing circuit through private magnet 171. This circuit extends from ground G springs 172 and 173 and magnet 171 to battery, thence through battery to ground. The relay 164- being a slow relay does not det nergize during the momentary breaking of its circuit. between impulses, but does dc'energize at the end of the operation of the substation dial for the second digit, thereby permitting the private magnet to also deiincrgize, which allows the side switch to pass to second posi tion.- The side switch, in passing from first to second position, disconnects the battrry from the vertical magnet 14-7 and closes a circuit through the rotary magnet 174. This circuit extends from ground G through interrupter springs 17!, rotary magnet 174, relay 176 and side switch wiper 165 to battery lead 67, thence through battery B to ground. The rotary magnet, upon energizing, operates to rotate the wipers one step, to press down the private magnet armature, and to open its own circuit at the interrupter springs 175. When the retary magnet circuit is thus opened the rotary armature falls back. If the first trunk upon the contacts of which the wipers have just been rotated is not busy the private armature follows the rotary armature and permits the side switch to pass to third position. If the first trunk is busy. however, the shaft will be rotat another ll. ,Eiltlalmll. w

contact, just as described for the first selector. As the side switch passes to third position the wiper 178 places a guarding potential onthe private bank contacts. This extends from ground G through springs 179 and 180, wiper 17 8 (in third position) and private wiper 1215 to the private bank contacts. This potential serves to keep another switch from stopping on a corresponding contact during the time that the side switch wipers are passing to the third position, and also during the time that the relays 73 and 181 of the connector are energizing. As soon as the relay 181 energizes it places a guarding potential back over conductor 183, to replacethat just described, as soon as the slow relay 176 deenergizes, and also supplies a ground for the release relay 166 of the second selector H. Therefore, the holding circuit for relay 166 now extends from ground G through side switch wiper 188, springs 190 and 189 to conductor 183, shaf wiper 145, side switch wiper 178, springs 180 and 191 to and through relay 166 to battery. As soon as the side switch wipers 133 and 139 pass to third position, the trunk lines 134 and 138 are extended to the trunk lines 1841 and 182 which lead to the connector T. The extension of these trunks completes an energizing circuit through the double wound line relay 73 of the connector. This circuit extends from ground 13? through the side switch wiper 192, lower 'winding of relay 78, springs 198, and 194:,

conductor 184, selector wiper 146, side switch wiper 133, conductors 134 and 185, thence through relays 136 and 72 ot the repeater F in the same manner as traced for the relay 132, thence back over trunk conductors 13 8 and 182, through springs 195 and 196,

and upper winding of relay 73 to battery lead 140. The relay 78, upon energizing,

operates to close an energizing circuit torrelay 181, which in turn energizes and err tends a ground connection back over the conductor 183, as already described. The

relay 181 also maintains the circuit of release magnet 77 open by separating springs 197 and 198, and connects the impulse spring 185 with the vertical magnet 741- through the springs 197 and 199 and. relay 200.

The foregoing is the operation of the apparator for the first two digits. The connector 1 is now in position to respond tothe operation of the substation calling device for the third digit 2. The operation of the calling device for this digit twice breaks the circuit of the repeater relay 68. The relay 68 operates to repeat two impulses to the connector line relay 73 in the same mannor in which two impulses were repeated to the relay 132 for the second digit. Each time the relay 73 di /energizes a circuit is closed extending from ground G through springs 186 and 185, 197 and 199, relay 200, vertical magnet 74: and side switch wiper .201 to battery lead 140. The vertical mag:

does not denergize during the momentary interruption of the current by springs 185 and 186, but does deenergize after the two impulses are sent in, thus permitting the private magnet to deenergize, which allows the side switch to pass to the second posi tion, The release magnet 77' is connected to battery inthe same manner as in the so lectors that is, after the shaft is raised from its lowest position, the arm 208 permits'springs 209 to engage spring 210, thus connecting said magnet to battery.

As the side switch wiper 201 passes to second position, battery is disconnected from the vertical magnet 74 and connected to the rotary magnet 75. The apparatus is now ready for the last digit U. The relay 73 responds, as before, to the breaking of its circuit by the repeater, in response to the substation calling device, to operate the rotary magnet 75 over practically the same circuit as it did the vertical magnet 741. The rotary magnet operates to rotate the shat't and shaft wipers ten steps onto the terminals of the called line #2220. H the called line is not busy the private magnet deenergizes and permits the side switch wipers to pass to third position. When the wiper ,188 passes to third position, the holding ground for relay 166 of the selector H is shift ed from ground G to ground G 3. The passing of wiper 192 to third position shifts the circuit of relay 73 from ground G to ground G thus placing the high resistance relay 79 in series with the relay 73. The relay 79 energizes ta place the springs 211 and 212 in engagement, thus connecting ground Gr onto the relay 181 in case the relay 73 should deenergize-sutficiently to allow its armature to fall back,

and, by enga ment of springs 216'and 217, extends the due conductor 218 from wiper 1th 202 to the called substation. The wiper 213 also connects ground to the relays 77 and 81. The wiper 220 (inthird position) extends the conductor 225 from the ringer relay springs to the called substation. The wiper 201 (in third position) places battery on therelay 77 and also completes an energizing circuit for the ringer relay 78. This circuit extends from ground G through interrupter 221, relay 78, springs 223 and 222 and wiper 201 to battery B, thence through battery to ground. The relay 78, upon energizing. disconnects the calling and called lines and connects the ringer generator L with the called line to ring the bells 224. Since the circuit of the ringer relay includes the interrupter 221, the said relay is energized only intermittently so as not to ring the called substation continuously. When the called subscriber removes his receiver, or as soon thereafter as the ringer relay deenergizes, if it happens to be energized at the time, the called substation is provided with talking current-over a circuit extendin from ground G through side switch wlper 213, lower winding of relay 77, conductor 225, springs 227 and 226, side switch wiper 220, shaft wiper 204, conductor 219, springs 228 and 229, impulse springs 230, receiver 232, transmitter 231, springs 216 and 217, conductor 218, wiper 202, springs 233 and 234, 235 and 236, upper winding of relay 77 and wiper 201 to battery B, thence through battery to ground. The relay 7 7 upon energizing, short-circuits the high resistance relay 79 by the closure of springs 300 and 301, and completes an energizing circuit through relay 81 by the engagement of springs 237 and 238. This circuit extends from ground Gr through wiper 213, relay 81 and springs 237 and 238 to battery. The energization of relay 81 performs three functions: First, the engagement of the springs 239 and 222 forms a locking circuit for the relay 81, which circuit extends from ground G through side switch wiper 213, relay 81, springs 239 and 222 and side switch wiper 201 to battery lead .140. Second, the disengagement of springs 222 and 223 breaksthe energizing circuit of the ringer relay. Third, the engagement of springs. 194 and 195 with springs 247 and 246, respectively, reverses the direction of the current flowing over conductors 182 and 184. As a consequence thedirection of the'flow of current through the upper winding of relay 72 of the repeatenl? is reversed, which relay now attracts its armature to bring springs 125 and 126 into engagement with springs 248 and 249, respectively. The engagement of these springs reverses the direction of the fiov of current over conductors 120 and 121, but. as in the connector, it does not reverse the direction of the current through the doublewound line relay. This reversal of the current in the coiiductors 120 and 121 causes the attraction of the meter magnet armature 62, as the current of the two windings of relay 63 are now assisting each other. The attraction of this arn'lature causes the meter to register once by means of the pawl on the armature 62 engaging the ratchet Wheel 61 of the meter. It will be remembered that the relay 81 of the connector controls its own circuit; therefore, the meter will only register once no matter how many times the receiver at substation A is lifted from its hook. The attraction of the armature 62 also closes the springs 66 and 67 into engagement, thereby short-circuiting the winding 64, but as the winding 65 is still energized it serves to hold the armature 62 in an operated position.

After the conversation is completed the release of the central ofiice apparatus used in the connection is initiated by the restoration of the receiver-at the calling substation. When the springs 85 and 87 of substation A are disengaged by placing the receiver on the hook, the energizing circuit of the relay 68 of the repeater F is broken, thus allowing it to denergize. The separation of springs 128 and 129 breaks the energizing circuit of the relay 69. This relay deenergizes to disconnect the holding ground from the release relay 101 of the selector E. The de'c'nergization of relay 101 closes an energizing circuit through the release magnet 57 over the following circuit: Ground G springs 98 and 99, 103 and 102, magnet 57 and springs 58 and 59 to battery. This circuit is broken again by the springs 58 and 59 when the shaft reaches its lowest position. The deenergization of relay 101 also breaks the holding circuit of the winding 17 of line switch C, which deenergizes and allows the plunger arm to be restored .to normal position, thus breaking the energizing circuit of the winding 65 of the meter magnet, whose armature is also restored to normal position. The release of the second selector and connector is quite similar to that of the first selector. The deenergizing of the line relay 68 of the repeater F opens the circuit of the line relay 73 of the connector, which deenerziges to break the holding circuit of the release relay 181 of the connector and of relay 166 of selector H. The relay 166, upon deenergizing, closes the circuit of the release magnet 167, as in the first selector E. The engagement of springs 197 and 198 of relay 181. closes a circuit through the release magnet 77 of the connector over the following circuit: ground G springs 186 and 185, 197 and 198, magnet 77, springs 209 and 210 to battery B, thence through battery to ground. The connector, upon restoring to normal position, breaks the circuit of the winding 214 of line switch 0 at the private aerator wiper 203-; thus all the switches are now in readiness for another call.

In case a line is already busy when called,

- the calling subscriber is given the busy sig- 80. springs 207 and 206, and private magnet 76 to battery lead 140. The spring 206 engages springs 207 before it breaks contact 'with spring 205, and thus the energizing circuit of the private magnet is not broken when the relay 200 deenergizes. The private magnet therefore remains energized, locking the side switch in second position, and at the same time relay 80 is energized in series therewith. When relay 80 energizes, the

spring 242 engages spring 241 beforebreaking A contact with spring 243, thereby shifting the holding ground for relay 80 and private magnet 76 from the private wiper203 to ground G. This circuit extends from ground G through side switch wiper 188, springs 190 and 189, springs 241 and 242, relay 80, springs 20? and 206 and magnet 7 6 to battery. The disengagement of springs 230 and 240 of relay 80 breaks the circuit of the rotary magnet 75. The calling subscriber now receives the busy signal over the circuit extending from battery through secondary winding of induction coil 83, springs 245 and 244:. side switch wiper 220, springs 226 and 227. conductor 184, through substation A, back over conductor 182, springs 195 and 196, upper Winding of relay 73, thence to the battery lead to the starting point. The primary busy circuit extends from ground G through an interrupter 82, primary or induction coil 83 to battery, thence through battery to ground. -While the calling subscriber is receiving the busy signal, the con nection with the called line is open on one side at the side switch wiper 220, and on the other side at the private magnet springs 235 and 236. The switches are released from this position by the hanging up of the receiver at the calling substation in practically same manner as when the called line was The rotary connector I shown in Fig. 4: is, as before mentioned, quite similar to the connector switch shown in Fig. 3. The rotary connector switch is controlled by the calling subscriber over'trunk lines leading from the banks of the selector H. The repeater lF. works in conjunction with this rotary connector the same as with connector T. This type of connector is used where a business house or private branch exchange, for instance, desires to have a plurality of trunk lines extending to the central ofice, but wishes to be given only one number. This connector is so arran ed that if the first of these trunks or lines is in use, it will automatically extend the calling subscribers line into connection with the second line; if the second line is also busy the connection will be extended to the third line, and so on. The calling subscriber would, of course, have no control over the apparatus as to with which one of the lines he may make connection. This, however, does not concern him, since any trunk line to the said office or private branch exchange will serve his purpose. The arrangement of the. con nector banks will be as follows: Suppose, for instance, that the office or business house to which the number 2121 has been assigned wishes three telephones, it will be given three lines, one terminating in the first contact of the second level of the connector banks, the second in the second contact of the second level, etc. Now suppose, for instance, that the substation A, instead of calling #2220 as was heretofore described, calls the number 2121. The action of the line switch, first selector and repeater is the same as before. The shaft of the second selector, however, instead of being raised two steps as before, will, in response to the calling device for the second digit 1, be raised only one step and, as before, automatically rotated one step onto the terminals of a trunk line leadin to the said rotary connector. The operation of the connector in response to the calling device for the last two digits is as follows: The circuit of the double-wound relay 248 is broken twice in response to the calling device, or, more strictly speaking, since the calling device controls the repeater, in response to the repeater. The deenergizing of relay 2t8 closes an energizing circuit through the vertical magnet 249 in series with the slow relay 84. The circuit extends from ground G through springs 251 and 250, 252 and 253 (as the relay 254: is energized), slow relay 84, vertical-magnet 249 and side switch wiper 255 to battery lB, thence through battery to ground. The vertical magnet energizes to raise the shaft and shaft wipers two steps opposite the second level of bank contacts. T e energizin of the relay 8t closes an energizing circuit through the private magnet 256, which relay, upon deenergizing, allows the side switch to pass to second position. The passing of the s 1de switch wiper 255 to the second position switches battery from the vertical magnet 249 to rotary magnet 269. The calling device is now operated for the last digit (,1). The rotary magnet responds by rotating lllh rat

the shaft one step onto the first bank contact. As before stated, this is the first of the lines leading to the called subscriber. If this contact is not busy the side switch passes to third position in the usual manner, completing the line connection to the called substation and placing a guarding ground on the private bank contact over a circuit extending from ground G through side switch wiper 257, relay 258, springs 259 and 260 to private wiper 261. This pre vents another connector from stopping on this contact. In case the first contact is busy, however, the wiper 261 will find the first contact grounded. Then, as soon as the relay 84 deenergizes, a circuit is completed extending from the ground at the private wiper 261 through springs 260 and 259,'relay 258, side switch wiper 257 (in second position), springs 263 and 262, private magnet 256 to battery, thence through battery to ground. The relay 258 does not energize over this circuit. The private magnet 256, however, remains energized after relay 84 deenergizes, completing a circuit extending from ground G through interrupter 264, springs 265 and 266, 267 and 268, rotary magnet 269 and side switch wiper 255 (in second position) to battery 13, thence through battery-to ground. This interrupted current through the rotary magnet operates to energize the rotary magnet, which in turn rotates the shaft one step onto the second bank contact. If this contact is idle the private magnet deenerglzes and the side switch passes to third position in the usual manner. If the second contact is also busy the shaft will continue to rotate until the private wiper finds an idle contact. Should all of the trunk lines be busy the subscriber is given the busy signal as follows: The shaft wipers are rotated over all of the busy trunk lines, such as 270, 271, and 272, but stop on the next adjacent contacts 273, 274 and 275. The private contact 274 is connected through a resistance to'b'attery. The contact 273 may be dead, while the contact 275 is connected through a relay 276 to battery. As the connector wipers pass onto the contact 274 the private wiper is shifted from round to battery through the resistance 27 This allows the private magnet to deenergize, which in turn allows the side switch to pass to the third position. A circuit is then completed extending from ground G through the side switch wiper 257, relay 258, springs 259 and 260, private wiper 261 and resistance 277 to battery B. The relay 258, upon energizing, causes the spring 259 to engage the spring 278 a short time before breaking from the spring 260. This is to allow a new circuit to be established through the relay 258 before the old circuit is broken. This new circuit extends from ground G through the relay 258, springs 259 and 278, private magnet 256 to battery. Although the current flowing through the relay 258' thus allowing another subscriber to also stop .on the contact 274 that he may receive the busy signal. The relay 276 energizes over a circuit extending from ground G through the lower winding of the relay 279, ringer springs 281 and 280, side switch wiper 282, shaft Wiper 283, contact 275 and relay 276 to battery, thence through battery to ground. This relay, upon energizing, gives the subscriber the busy signal over the following circuit: battery, secondary of induction coil of the busy machine 0, springs 285 and 284, contact 275 and wiper 283, then over the same circuit as described in connection with the connector I. The other features of this connector are essentially the same as in the connector I. Of course, it is evident that another group of lines could be connected to the contact beginning with the set of contacts following the contacts 273, 274 and 27 5. To obtain connection with one of these lines it would be necessary to call #2125, assuming contacts 273, 274 and 275 are the fourth set, as shown in the drawings. As shown in Fig. 5. the cord Cll' cuit R consists essentially of the answering plug 1) and calling plug 7), supervisory relays 287 and 288, lamps 289 and 290, repeating coil N, key K, operators set M and calling device 291. A magneto telephone is also shown at substation A in Fig. 5.

It will now be explained how supervision is brought about in the cord circuit in case the subscriber at the manual substation A calls the subscriber A. The subscriber A removes his receiver and operates the hand generator 292 in the usual manner, which places a chrrent on the conductors 293 and 294 to operate the drop 295. The operator inserts the plug 2 into jack 7' in response to the signal, and throws the key K, thereby cutting her set into the circuit. Upon learning the, number desired by the calling subscriber, the operator inserts the plug p into the jack j. The trunk conductors 298 and 299 of the jack 7" lead to a line, switch C in the same manner that the line conductors 12 and 13 lead to the line switch C. The line switch C is in all respects similar) to the line switch C, except that the normal conductors may be omitted. The line switch C has access to first selector switches in the same manner as the line switch C, through the mediu'm of which the operator is enabled to set up any desired automatic connection.

tti

ttti

lid

tth

tttt

reenter.

th y throwing the trey l t the epereter distennects the tettting set M end windings 2% end 297 ct the repeeting coil tit trem ecress the trunh conductors eee end Q99, end con nects the ceiling device 291i eeress the trunk insteed, 'the epereter new sets up the cell threugh the line switch "C setecter ht repeeter h, selector t-t end e connector t in enectty the sense menner, end the eperetien et? seid switches is the seine es when the suhscriher et suhstetien rt celled suhstetien 1th tlt wi'tt he rememhered thet when the cen necter side switch 192 pe ed trem. second te third positien the high resistenee reley t9 wes included in series with the deuhteweund tine reley td, end consequently in series with the rete vs the end t2 oi the re peeter it. 'the retev res dees not receive enough current when connected. in series with retey 79 to he eperetivet v energised; consequently, when the reley in ot the re peeter deenergiees etter the test digit is celled the high resistence retey it is in eluded in circuit with the deuhte-wound tine reley es. When the epereter restores the her it etter cempteting the cett the retey see is hridged ecress the line end thus is connected in e series circuit with rete vs it end es et the repeeter it. "the retep 28h dees not receive enough current when eon-- nested in series with retep 7t te he eperetivety energised end does not hreetr the cir cuit ot the temp 29 which wes ctesed es seen es the plug p wes inserted inte inch: 1 "this circuit eetends trern greund Gt through sleeve et iectt t end plug p, springs tttth end httt, centect see ermeture ees end temp 290 to hettery id, thence through the hettei te ground. the energieetien oi the reley (t et the repeeter t provides e new hetdin ground tor the rete v ee, meinteins the hridge ecross the truntr conductors tht end 1355 closed end prevents the ctesure oi the circuit et retey m in cese the line retey es etlewed its erineture to tell hectr when ret ey t't enters its circuit en the celled suh scriher reeves his receiver the hectehridge retep it 'energiees end short-circuits the retey (9 in the seine inenner es when suhstetien 1t. wes celled hp suhscriher et suhste tien hi. en the retey 719 is short-circuited it reduces the resistence oi? the circuit et retey thhwet' the repeeter t sutticiently to ellew seid retey to operetivelgv energize. the ener'eetien e't retey the serves te shortcircuit the rele v 'tt, which reduces the resist ence ct the circuit ct the repeeter tine retey es end e't the supervisory rete v 28% et the cord R suhficientlv te ceuse these reteys to he eperetivet energised. "the energieetien ct retey 288 greehs the energiein circuit oil the temp 290., which signifies te t e epereter thet the celled suhscriher hes. enswered. en the celled suhscriher hengs up his receiver upon the terminetien et t e eeuvei entice, the connector hectehridge retey it deenergiees end removes the short-circuit iretn rete'v 1th., the retey t9 thus egein enters the circuit sit the reley tBh, which then etlews its erineture to tell hectr, removing circuit oi temp 290'. The line switch t3 is provided with e meter like the meter J (Fig. l) This meter is epereted hy the reversed of I the current when the celled suhscriher removes his receiver in the serne menner es eirpteined ter the meter d when e cell wes needs trern suhstetion it.

hupervision in the ether side et the cord is telren cere ct hy the retey 28ft in the usuet nlenner. this rete is energised through its right-heed winding hy current irons the suhstetien generetor 292. "t tthen the reley set is thus energised it terms e inching cir cuit tor itsett extending trom ground it threugh sleeve ct tech 3; end plug p, springs 3th end see, contect 311 end winding St); to hettery id the temp 289 is then lighted ever e circuit extending trom ground G through steeve et tech: 3' end plug p, centect 3th end temp see to hettery tt, Upon the removet et the pin s :trem the techs both temps ere entinguishec end the selector and connector switches end. the repeeter ere restered te nermet esitien, just es when the receiver et the cel ing suhstetien it wes restored te the switch heolrin the first connection descrihedi it will he noted thet the retery connector t is supptied with e high resistence reley 314i which is simiter to relep t9 ct cennecter it, end e supervision is ohteined through cennecter t in, the sense menner esfthrough connector t,

tt will he understeed, eit course, thet the supervisory reteys t9 end tit ct" the connector it end repeeter t eperete in the seine menner when en euternetic suhscriher cells es when e menuel epereter sets up the cell. "the eperetien et these retevs is without enjp perticuter itunctien, however when the ce t comes 'trem en eutemetic suhstetion, es the insertion ot-e resistence in the line hetere e suhscriher enswers hes ne sheet on the meters;

lhrem the iloregoing it will he seen thet provide e system in which the subscribers ere given meesured service end in which tell is essessed hy e mecheuisrn which is respensive tn the reverset. ct current .in the tetlting circuit. The reverset oi the current niey he in the ceiling suhserihers line, or in e pert et the tettring circuit hetween the ceiling end celled lines, depending upon the conditions end requirements or any perticuter cese, her this purpose, es eepleined, e ceecter is previded heving ineens tor tlttt tttti reversing the current in the talking circuit .that is to say, in that portion of the talking circuit which is between the calling subscriber and the connector.

The said connector may be one for ordinary use, or it ma be a rotary connector of the kind shown an described. Furthermore, the said connector may be of the kind in which provision is made for decreasing the flow of current in the talkin circuit when the called line is found to in icate to an operator that the connection has been established, and for then retiring the supervisory signal when the called subscriber answers. Thus two thin may be accomplished by the response of t e called subscriber, to-wit, the giving of a supervisory signal and the registering of the call, or the operation of any other suitable mechanism for any suitab e purpose. 'Furthermore, it is obvious that the reversal of current in the talking circuit may be accomplished by other suitable means, and not by means in the connector, without departing from the spirit of my invention. Any automatic switch for use in an automatic or semi-automatic tele hone exchange system which has provision or reversing the flow of current in the talking circuit will serve the purpose of my invention. Also, it will be seen that my invention is operative in connection with a system in which the automatic switches are controlled over metallic circuit's-that isto say, by controlling the two sides of the calling lme in series. Again, it is preferable that my improved system be of the kind in which the current for talking purposes is supplied from, a central source, or from one or more central sources, when the call is from one automatic subscriber to another. As shown, however, local batteries may be employed for the" manual substations, and it is contemplated that other arrangements may be em loyed for supplying talking current wit out departing from the spirit of my invention.

It will be'seen that the selectors and connectors of my improved system are of that type in which one motion is employed for se ecting a group and another motion for tlien finding a line in the predetermined group. In the selectors, for example, the vertical motion is employed for selectin a group of trunks corresponding to the digit of any calledhumber, and the rotary motion is then employed for automatically selecting an idle trunk in the predetermined group. In the connectors the vertical mo tion is employed "for selecting a grou of subscribers lines inaccordance with a igit of the called number, and the rotary motion is then. employed for finding the called line in accordance with another digit of the callednumber. The system is of the twowire type, to-wit, a system which is free from operating grounds at the substations thereof. As described and illustrated, the calling connection may be either entirel automatic or semi-automatic, and in the atter case the originating operator has complete supervision of the connection. In either case, however, the call is registered by a measured service device of any suitable character which responds to a reversal of current in the talking circuit when the called subscriber answers. The measured service device may be located at any suitable point in the connection, dependin upon the purpose for which it is employed? In telephone systems giving so-called meansured service, it is very often desired that no charge shall be levied for calling certain lines, such as lines which terminate at the central office and over which operators or exchange attendants are callcd,. .etc. In systems employing meters which are operated automatically when the called subscriber answers, this requires that special means be provided to prevent the meter ot the calling line from being operated when a call to a free line is answered. This may be very easily accomplished in the system shown herein by making all such lines which are to be called freeaccessible by special connector switches. -This special connector can be merely the ordinary form of twowire connectorthat is, a connector which does not have any provision for reversing the current upon the line. For example,

these special connectors may be similar in.

all respects to the connector I (Fig. 3), with the exception that the windings of the line relay 73 should be connected to the trunk conductors 182 and 184 direct and not through the springs of the relay 81. The relay 81 of these special connectors would then have no springs corresponding to the springs 193, 194, 24.7, 196, 195 and 246. When any line is called over such a connector, the response at the called substation does not cause the current in the calling line to be reversed, and consequently the meter of the calling line is not operated. Thus, any line in the system can call any line which is accessible from these special connectors without being charged for the call.

What I claim as my invention is: 1. In a telephone system, a manual switchboard, means including a repeater and a connector for extending connection therefrom, said connector and repeater provided with means for reducing the flow of current in the talking circuit when the called line is found, a signal at the manual switch board, which signal is responsive to said reduction of current in the talking circuit, and means for retiring said signal when the called subscriber answers.

2. In a telephone system, a manual switch board, means including a repeater and a integer connector tor extending connection there till tilt

trom, said connector and repeater provided with means for reducing the fiow of current in the talking circuit when the called line is tound, a signal at the manual switch-- board, which signal is responsive to said reduction of current in the talking circuit, means for retiring said signal when the called subscriber answers, and a central source of talking and operating current.

3. in a telephone system, a manual switchboard, means including a repeater and a connector for extending connection there- '"lrom, said connector and repeater provided with means tor reducing the flow cit current in the talking circuit when the called line is tound, a signal at the manual switchboard, which signal is responsive to said reduction oil current in the talking circuit, and means for retiring said signal when the called subscriber answers, said system being tree from operating grounds at the substations thereot,

l. in a telephone system, the combination with an operators position and a called telephone line, oi means tor extending a connection therebetween, a supervisory signal at the operators position, a plurality of serially related closed supervisory control circuits, a marginal relay in the first of said circuits controllingsaid signal, a mar ginal relay in the second of said circu ts controlling the resistance oi the first circult, and means controlled over the called line tor controlling the resistance ot'said second circuit. a

5. in a telephone system, an established connection extending through an operators position and including a plurality oil serially related trunk lines and a called telephone line, a plurality of serially related closed supervisory control circuits each including a trunk line conductor, a supervisory relay at the operators position in the first oi said circuits and irresponsive to the normal current fiow therein, means controlled over the called line for increasing the current fiow in the second 0t said closed circuits, and a marginal relay responsive to such current increase for in turn increasing the current in said first circuit. a

tl. lln a telephone system, an established connection extending through an operators position and including a plurality oi serially related trunk lines and a called telephone line, a plurality of serially related closed supervisory control circuits each including a trunk line conductor, a supervisory relay at the operators position in the first of said circuits and irresponsive to the normal current fiow therein, means controlled over the called line tor increasing the current :tlow in the second of said closed circuits, a, marginal relay responsive to such current increase tor in turn increasing the current in said first circuit, whereby said supervb sory relay may be operated, and a signal controlled by said relay.

i. In a telephone system, an established \connection between a calling and a called line including an operator-" cord circuit and a, plurality of trunk lines, serially related closed supervisory control circuits each including a trunk line conductor, a supervisory relay in the first of said closed circuits sensitive toresistance changes therein, means controlled over the called line for alterin the resistance ot the other or said close circuits, and means responsive to such alteration oi resistance tor alterin the resistance of said first circuit to a bot said relay,

ii. in a telephone system, an established connection between a calling and a called line including an operator s cord circuit and a plurality oi trunlr lines, serially related closed supervisory control circuits each including a trunk line conductor, a super visory relay in the first of said closed circuits sensitive to resistance changes therein, a second relay controlled ever the called line tor altering the resistance oi? the other out said closed circuits, a third relay resport sive to such alteration ct resistance tor altering the resistance ot said first circuit to operate said first relay, and a signal'in said cord circuit controlled thereby.

9. in a telephone system, an established talking connection between a calling and a called line including an operators cord circuit and an automatic switch, serially related closed supervisory control circuits each including a talking conductor, a supervisory relay in the first at said circuits sensitive to resistance changes therein, and a relay in the second of said circuits sensitive to resistance changes therein tor altering the {resistance of the said first circuit,

10.. In a telephone system, an established itallring connection between a calling and a called line including an operators cord cir cuit and an automatic switch, serially related closed supervisory control circuits each ineluding a talking conductor, a supervisory relay in the first of said circuitssensitive to resistance changes therein, a relay in the second of said circuits sensitive to resistance changes therein tor altering the resistance ot the said first circuit, and means controlled over the called line tor altering the resistance of said second circuit.

ll. lln a telephone system, an established talking connection between a calling and a called line including an operators cord cit cuit and an automatic switch, serially reltlli llll llli

it it'll lated closed supervisory control circuits each including a talking conductor, a supervisory relay in the first ct said circuits sensitive to resistance changes therein, a relay in the second at and circuits sensitive to resistance changes therein for altering the resistance of said first circuit, and a relay in said switch controlled over the called line for altering the resistance of said second circuit.

12. In a telephone system, a temporarily established connection comprising three inductively connected sections, including, respectively, an operators cord circuit, an automatic switch, and a called telephone line, serially related closed supervisory control circuits including, respectively, conductors of the first two sections, a third circuit including a conductor of the third section, a supervisory relay in the first circuit, and means in each circuit except the first for effecting a change in the resistance of the preceding circuit, whereby said supervisory relay may be controlled from the called substation.

13. In a telephone system, a temporarily established connection comprising two inductively connected sections, an operators cord circuit and a trunk line included in the first section, an automatic switch and a called telephone line included in the second section, a supervisory relay in said cord circuit, a closed circuit for said relay including a conductor of said trunk line, and means actuated upon the response of the called subscriber for altering the resistance of said circuit to control said relay.

14. In a telephone system, a temporarily established connection comprising two inductively connected sections, an operators cord circuit and a trunk line included in the first section, an automatic switch and a called telephone line included in the second section, a supervisory relay in said cord circuit, a closed circuit for said relay including a conductor of said first section, a second circuit including a conductor of said second section, and a second relay controlled over said second circuit for altering the resistance of said first circuit to control said first relay. 15. In a telephone system, a temporarily established connection comprising two inductively connected sections, an operators cord circuit and a trunk line included in the first section, an automatic switch and a called telephone line included in the second section, a supervisory relay in said cord circuit, a relay in bridge of said first section controlling said switch, a circuit includin said relays in series, and means controlle over the said second section for altering the resistance of said circuit to control said supervisory relay.

16. In a telephone system, a temporarily established connection comprising two inductively connected sections, an operators cord circuit and a trunk line included in the first section, an automatic switch and a called telephone line included in the second section, a supervisory relay in said cord circuit, a circuit for said relay including a conductor of said first section, a resistance in said circuit 'endering said relay inoperative, and a relay controlled over a conductor of the other section for short-circuiting said resistance.

17.. In a telephone system, a temporarily established connection including an operators cord circuit, a trunk circuit, and a plurality of serially related automatic switches connecting said trunk circuit with a called line, a relay in bridge of said trunk circuit controlling said switches, a supervisory relay at the cord circuit, a circuit including said relays in series, and means actuated upon the response of the called subscriber for altering the resistance of said circuit to control said supervisory relay.

18. In a telephone system, a temporarily established connection including an operators cord circuit, a trunk circuit, and a plurality of serially related automatic switches connecting said trunk circuit with a called line, a relay in bridge of said trunk circuit controlling said switches, a supervisory relay at the cord circuit, a circuit including said relays in series, a resistance in said circuit, said supervisory relay rendered inoperative thereby, and means actuated upon the response of the called subscriber for short-circuiting said resistance.

19. In a telephone system a temporarily established connection including an operators cord circuit, a trunk circuit, and a plurality of serially related automatic switches connecting said trunk circuit with a called line, a relay in bridge of said trunk circuit controlling said switches, a supervisory relay at the cord circuit, a circuit including said relays in series, said circuit including also a resistance whereby said last relay is rendered inoperative, and means controlled over the called line for shunting out said resistance, whereby the said last relay is enabled to operate.

20. In a telephone system, a connection between a calling and a called line, a signal for indicating the response of the called subscriber, two cooperating closed control circuits in serial relation to each other, means controlled over the called line for altering the resistance of the. last of said circuits, means responsive to such alteration for in turn altering the resistance of the first of said circuits, and means in said first circuit for controlling said signal.

21. In a telephone system, a connection between a calling and a called line. a signal for indicating the response of the called subscriber, two cooperating closed control circuits in serial relation to each other, means controlled over the called line for altering the resistance of the last of said circuits, means responsive to such alteration for in turn altering the resistance oi": the first of said circuits, and means in said first cirdill till

till

snail tor cutting said resistances in or out of said circuits. 7

22. In a telephone system, a line, an auto matic switch for said line having hank terminals divided into groups, the groups being disposed in parallel planes, movable arms having motion in one direction to find a group and motion in another direction to find a terminal in the selected group, a line relay for controlling the operation of said arms, means for controlling the two sides of said line in series to control said relay, a local circuit governing the said second motion, normally closed contacts in said local circuit, which contacts are open during the said first motion, and means whereby said contacts are then closed to control the second motion.

23. lln a telephone system, an automatic switch having bank terminals divided into groups, the groups being disposed in par allel planes, movable arms having motion in one direction to find a group and motion in another direction to find a terminal in the selected group, an electromagnet tor producing the first motion, an electromagnet for producing the second motion, means for controlling the two sides otsaid line in series to control one ofisaid magnets, a local circuit governing the said second motion, normally closed contacts in said local circuits, which contacts are open duringthe said first mo- .tlon, and means whereby sald contacts are then closed to control the second motion.

2a.. ln a telephone system, an automatic switch having bank terminals divided into groups, the groups being disposed in parallel planes, movable arms having motion in one direction to find a group and motion in another direction to find a terminal in the selected group, electromagnet mechanism tor producing said first and second motions, a

local circuit governing the said second motion, normally closed contacts in said local circuit, which contacts are open during the said first motion, and means whereby said contacts are then closed to control the sec ond motion.

25. ln a telephone system, an automatic switch having bank terminals divided into groups, the groups being disposed in parallel planes, movable arms having motion in one direction to find a group and motion in another direction to find a terminal in the selected group, a line relay for controlling the operation oi. said arms, means tor con trolling the two sides of said trunk in series to control said relay, a local circuit governing the said second motion, contacts in said local circuit, which contacts are open during the said first motion, means whereby said contacts are automatically closed upon.

the cessation of the first motion to control the second motion, other contacts in said local circuit, and means whereby said other contacts are automatically opened to stop said second motion when the said terminal is tound.

26'. lln a telephone system, an automatic switch having bank terminals divided into groups, the groups being disposed in parallel planes, movable arms having motion in one direction to find a group and motion in another direction to find a terminal. the selected group, an electromagnet tor producing the first motion, an electromagnet for producing the second motion, means tor controlling the two sides ot said line in series to control one of said magnets, a local circuit governing the said second motion, contacts in said local circuit, which contacts are open during the said first motion, means wherehysaid contacts are automatically closed upon the csssation oi? the first motion to control the second motion, other contacts in said local circuit, and. means whereby said other contacts are automatically opened to stop said second motion when the said terminal is tound.

27. ln a telephone system, an automatic switch having bank terminals divided into groups, the groups being disposed in par allel planes, movable arms having motion in one direction to find a group and motion in another direction to find a terminal in the selected group, electromagnet mechanism tor producing said first and second I motions, a local circuit governing the said second motion, contacts in, said local circuit, which contacts are open during the said first motion, means whereby said con tacts are automatically closed upon the cessation oi the first motion to control the second motion, other contacts in said local. circuit, and means whereby said other contactsare automatically opened to stop said second motion when the said terminal tound.

1th a telephone system, a linlr circuit tor extending connection between calling and called lines, fined terminals :t'or said link over which said linlr is seized, movable terminals tor said linlr tor entending the connection to a called line, a source at can rent, means tor supplying current to said fined terminals, means for supplying cur rent to said movable terminals, and means for reversing the current supply to said. movable terminals.

29. in a telephone system, a linlr circuit for extending connection between calling llll ltlli lllltl l l ll and called lines, fired terminals tor said link over which said linlr is seiaed, movable terminals for said linlr tor entending the connection to a called line, a source e t cur-- rent, means for supplying current to said fined terminals, means tor sup ilying current to said movable terminals, and means for reversing the current supply to said fixed and movable terminals.

30. In a telephone system, an automatic progressively movable switch for extending connection between calling and called lines, fixed terminals for said switch over which said switch is seized, movable terminals for said switch for extending the connection to a called line, a source of current, means for supplying current to said fixed terminals, means for supplying current from said source to said movable terminals, and means for reversing the current supply to said movable terminals.

Signed by me at ClllCiI/gO, Cook county, Illinois, this 10th day of larch, 1917.

TALBOT G. MARTIN 

